Effect Of Delayed Initial Feeding On The Digestive Enzymes Activities Of Odontobutis Potamophila Larval And Juvenile

The Odontobutis potamophila belongs to Perciformes, Odontobutidae. It is an important freshwater commercial fish in China. Some studies have been conducted in the biology and digestive system of the Odontobutis potamophila. The present paper was conducted to examine the effect of delayed initial feeding on the digestive enzymes activities, the quantities of mRNA expression of trypsin gene, oxygen consumption rate and NH3-N excretion rate of Odontobutis potamophila larval and juvenile. The main results are concluded as follows:1. Effect of delayed initial feeding on the digestive enzymes activities of Odontobutis potamophila larval and juvenileThe activities of the amylase, lipase, pepsin and trypsin of Odontobutis potamophila juvenile and larval were examined during delayed initial feeding and feeding. The result indicated that the amylase activity rase as the development of larval. Larval of feeding group arrived the highest activities of 0.1779 U/mg protein at 12 days after hatching (DAH), as the amylase activity of the delayed initial feeding group lower than feeding group. The delayed initial feeding group arrived the highest activities of 0.1844 U/mg protein at 15 DAH, when exceed the feeding group.The lipase activity of the delayed initial feeding group lower than feeding group(p < 0.05) from 0 DAH to 9 DAH. During that stages the lipase activity of feeding group kept the high level and arrived the peak time value that were 68.1964 U/mg protein. The lipase activity of the delayed initial feeding group were higher than the feeding group at 12 DAH when arrived the peak time value that were 43.8528 U/mg protein,and later dropped to below the feeding group level until the end of experiment.The pepsin activity of the delayed initial feeding group and the feeding group achieved the peak time value respectively that were 1.1326 U/mg protein and 0.8766 U/mg protein at 3 DAH. From 3 DAH to 12 DAH The pepsin activity of the delayed initial feeding group were higher than the feeding group all the time, but two groups of larval pepsin activities had significant differences only when 6 DAH (p < 0.05). The pepsin activity of the delayed initial feeding group decreased and were lower than the feeding group at 15 DAH, followed by an increase.The trypsin activities of Odontobutis potamophila larval and juvenile had two peak time values that the delayed initial feeding group achieved the first value which was 157.9169 U/mg protein at 6 DAH, followed by a decrease and lower the feeding group at 12 DAH (p < 0.05). Then it was increase and achieved the second peak time value at 18 DAH. After that the delayed initial feeding group was higher than the feeding group until the end of experiment.2. Effect of delayed initial feeding on the quantities of trypsin gene mRNA expression of Odontobutis potamophila larval and juvenileFluorescent quantitation PCR has been applied to examine the mRNA transcription level changes of trypsin of Odontobutis potamophila larval and juvenile. The results indicated that mRNA of trypsin of the delayed initial feeding group transcribe increased from 0 DAH to 6 DAH g, and it was 0.5297 at 6 DAH. This time the feeding group maintained lower level (p < 0.05). The feeding group was higher than the delayed initial feeding group significantly from 9 DAH to 18 DAH and achieved the peak time value that was 0.71577 at 15 DAH. At 9 DAH the delayed initial feeding group decreased the lowest value that was 0.02779, followed by a low level and an increase after 18 DAH.3. Effect of delayed initial feeding on oxygen consumption rate and NH3-N excretion rate of Odontobutis potamophila larval and juvenileOxygen consumption rate of Odontobutis potamophila larval and juvenile was measured with dissolved oxygen analyzer. Oxygen consumption rate of delayed initial feeding group and the feeding group increased with larval and juvenile development. The delayed initial feeding group and the feeding group had no significant differences at 0 DAH and 3 DAH(p>0.05). The delayed initial feeding group was lower than the feeding group from 6 DAH to 21 DHA, but from 18 DAH to 21 DHA the two groups had no significant difference (p>0.05). NH3-N excretion rate of Odontobutis potamophila larval and juvenile was examined, There were three stages about the change of NH3-N excretion rate. On the first stage delayed initial feeding group lower than the feeding group from 0 DAH to 6 DAH (p>0.05). On the second stage NH3-N excretion rate of the delayed initial feeding group higher than the feeding group significantly from 9 DAH to 12 DAH (p < 0.05). The last stage NH3-N excretion rate of the feeding group exceeded the delayed initial feeding group again from 15 DAH to 21 DAH, but had no significant differences (p>0.05). The feeding group achieved the peak time value that was 0.1877μg/(trail·h).